Fix bug 7054190 line breaks at inappropriate places

We were doing line breaks after punctuation as long as they weren't
surrounded by digits. This is a misinterpretation of the Unicode line
breaking algorithm. Punctuation (class IS) is not hugely different than
the default classes (NU and AL) - there are breaks after punctuation
that are allowed (for example, followed by an open parenthesis), but
we're not implementing the algorithm with anything near that level of
fidelity.

The long term fix is to really implement the algorithm. In the shorter
term, the easiest thing to do is to remove the special case altogether.

Change-Id: Ic4dc3216c2a4191fbb7cfa06e9dc038d1a56398c